• Mark's website with good practices https://www.goodemailcode.com/

text

<h1 style="margin: .67em 0; font-size:2em">Heading 1</h1>
<h2 style="margin: .83em 0; font-size:1.5em">Heading 2</h2>
<h3 style="margin: 1em 0; font-size:1.17em">Heading 3</h3>
<h4 style="margin: 1.33em 0; font-size:1em">Heading 4</h4>
<h5 style="margin: 1.67em 0; font-size:.83em">Heading 5</h5>
<h6 style="margin: 2.33em 0; font-size:.67em">Heading 6</h6>
<p style="margin: 1em 0;">Paragraph</p>

<a href="https://parcel.io" style="background-color:#005959; text-decoration: none; padding: .5em 2em; color: #FCFDFF; display:inline-block; border-radius:.4em; mso-padding-alt:0;text-underline-color:#005959"><!--[if mso]><i style="mso-font-width:200%;mso-text-raise:100%" hidden>&emsp;</i><span style="mso-text-raise:50%;"><![endif]-->My link text<!--[if mso]></span><i style="mso-font-width:200%;" hidden>&emsp;&#8203;</i><![endif]-->
</a>